MIAMI (AP) – Less than a week before trial, a onetime close associate of former U.S. Rep. David Rivera pleaded guilty Tuesday to four charges in a long-running campaign finance investigation that also implicates Rivera.

Attorneys for Ana Alliegro announced in a surprise that she would plead guilty rather than go to trial Monday. Prosecutor Thomas Mulvihill said there was no plea agreement requiring Alliegro to cooperate as a government witness against Rivera.

Her attorney, Richard Klugh, said there was no written deal in place.

"There is no guaranteed benefit for the plea. She's just accepted responsibility," he said.

Rivera, a Republican, has not been charged and has repeatedly denied wrongdoing. Alliegro, 44, was accused of funneling about $80,000 to an unknown Democratic candidate, Justin Sternad, in the 2012 primary for the House seat then held by Rivera. Prosecutors say the goal was to weaken Democrat Joe Garcia, who won anyway and later defeated Rivera in the general election.

Mulvihill said Tuesday for the first time publicly that Rivera was part of the conspiracy when asked for the name by U.S. District Judge Robert Scola. In the past, Rivera was identified only as "co-conspirator A" in court documents.

Rivera did not immediately respond to an email seeking comment Tuesday.

Earlier this year, Rivera filed papers to run for his old 26th District House seat again, then suspended his campaign in July. Recently, however, Rivera has been participating in campaign events such as a candidates forum over the weekend, and his name will appear on next Tuesday's GOP primary ballot.

Alliegro, meanwhile, is to be sentenced Sept. 10. The four charges against her each carry potential five-year prison sentences, but she is likely to get far less because she has now pleaded guilty and may cooperate in the ongoing investigation. Sternad also pleaded guilty and was sentenced to seven months in prison.

Alliegro has been jailed since her arrest in March in Nicaragua, where she had fled rather than plead guilty in fall of 2013. She had surrendered her passport to authorities but, unknown to them, she had a duplicate passport allowing her to travel to Nicaragua.

State prosecutors in Miami previously pursued up to 52 possible ethics and campaign finance violation charges against Rivera related to his personal use of campaign funds and a $1 million contract he had with a Florida gambling company, but investigators in 2012 decided to bring no charges in part because the statutes of limitation had expired.

Federal investigators were also looking into a possible tax evasion case stemming from the same allegations, but so far no charges have been filed.